It is known that most organic dyes are markedly unstable under the effects of ultraviolet (UV) radiation. This has significant undesirable consequences, including color fading and drift, in many articles of manufacture containing such dyes. In the photographic arts and other areas in which color fidelity is particularly important, the problems caused by effects of UV light on organic dyes, e.g. in film and/or prints prepared therefrom, are especially acute. For instance, at the time of film exposure in a camera, UV light can cause deterioration of sensitizing dyes involved in control of the visible light-induced silver halide reduction which forms the latent images for subsequent development. Thus, even in black-and-white photography, UV light has undesirable effects. In color photography, those effects of UV light can be significant, but are generally outweighed in importance by undesirable effects of UV light on image-forming dyes which color the finished print. Typical image-forming dyes tend to fade and/or change color substantially when subjected to substantial amounts of UV light, and when prints containing such dyes undergo prolonged exposure to UV light, very undesirable fading and/or drift of colors in the prints commonly results.
Much effort has been directed toward identification of substances which would stabilize organic dyes against UV light. For example, see U.S. Pat. Nos. 4,050,938 issued Sept. 27, 1977 and 4,042,394 issued Aug. 16, 1977 to W. F. Smith, Jr. et al, 4,045,229 issued Aug. 30, 1977 to W. W. Weber, II et al, 4,025,682 issued May 24, 1977 to R. F. W. Cieciuch et al and other references cited therein. Such efforts are complicated inasmuch as effectiveness of a given UV stabilizer varies considerably with the dyes to be stabilized and other characteristics of the articles containing those dyes; consequently it is very difficult to predict the degree of effectiveness of a given stabilizer or stabilizer candidate. Moreover, certain dyes are much more susceptible than others to undesirable effects of UV light. For example, the problems of color drift and fading are especially acute in articles containing azo dyes.
Accordingly, it is very desirable to identify substances which are more effective in stabilizing organic dyes against UV light, and it is an object of this invention to provide articles comprising an organic dye or precursor thereof and such a stabilizing substance. Another object is a method by which articles comprising an organic dye are efficiently stabilized against UV light. Another object is photographic elements which are stabilized against dye color deterioration by UV light. Another object is color photographic elements comprising organic dyes which are UV light-sensitive and a substance which is effective in stabilizing such dyes against UV light. Another object is azo dye-containing photographic prints having increased stability against UV light-induced color fading and/or drift. These and other objects will be further apparent from the following disclosure in which all parts and percentages are by weight except where otherwise noted.